nvme: provide optimized poll function for separate poll queues

If we have separate poll queues, we know that they aren't using
interrupts. Hence we don't need to disable interrupts around
finding completions.

Provide a separate set of blk_mq_ops for such devices.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/nvme/host/pci.c

@@ -1082,6 +1082,23 @@ static int nvme_poll(struct blk_mq_hw_ctx *hctx, unsigned int tag)
 	return __nvme_poll(nvmeq, tag);
 }
 
+static int nvme_poll_noirq(struct blk_mq_hw_ctx *hctx, unsigned int tag)
+{
+	struct nvme_queue *nvmeq = hctx->driver_data;
+	u16 start, end;
+	bool found;
+
+	if (!nvme_cqe_pending(nvmeq))
+		return 0;
+
+	spin_lock(&nvmeq->cq_lock);
+	found = nvme_process_cq(nvmeq, &start, &end, tag);
+	spin_unlock(&nvmeq->cq_lock);
+
+	nvme_complete_cqes(nvmeq, start, end);
+	return found;
+}
+
 static void nvme_pci_submit_async_event(struct nvme_ctrl *ctrl)
 {
 	struct nvme_dev *dev = to_nvme_dev(ctrl);
@@ -1584,17 +1601,25 @@ static const struct blk_mq_ops nvme_mq_admin_ops = {
 	.timeout	= nvme_timeout,
 };
 
+#define NVME_SHARED_MQ_OPS					\
+	.queue_rq		= nvme_queue_rq,		\
+	.rq_flags_to_type	= nvme_rq_flags_to_type,	\
+	.complete		= nvme_pci_complete_rq,		\
+	.init_hctx		= nvme_init_hctx,		\
+	.init_request		= nvme_init_request,		\
+	.map_queues		= nvme_pci_map_queues,		\
+	.timeout		= nvme_timeout			\
+
 static const struct blk_mq_ops nvme_mq_ops = {
-	.queue_rq		= nvme_queue_rq,
-	.rq_flags_to_type	= nvme_rq_flags_to_type,
-	.complete		= nvme_pci_complete_rq,
-	.init_hctx		= nvme_init_hctx,
-	.init_request		= nvme_init_request,
-	.map_queues		= nvme_pci_map_queues,
-	.timeout		= nvme_timeout,
+	NVME_SHARED_MQ_OPS,
 	.poll			= nvme_poll,
 };
 
+static const struct blk_mq_ops nvme_mq_poll_noirq_ops = {
+	NVME_SHARED_MQ_OPS,
+	.poll			= nvme_poll_noirq,
+};
+
 static void nvme_dev_remove_admin(struct nvme_dev *dev)
 {
 	if (dev->ctrl.admin_q && !blk_queue_dying(dev->ctrl.admin_q)) {
@@ -2276,7 +2301,11 @@ static int nvme_dev_add(struct nvme_dev *dev)
 	int ret;
 
 	if (!dev->ctrl.tagset) {
+		if (!dev->io_queues[NVMEQ_TYPE_POLL])
 			dev->tagset.ops = &nvme_mq_ops;
+		else
+			dev->tagset.ops = &nvme_mq_poll_noirq_ops;
+
 		dev->tagset.nr_hw_queues = dev->online_queues - 1;
 		dev->tagset.nr_maps = NVMEQ_TYPE_NR;
 		dev->tagset.timeout = NVME_IO_TIMEOUT;